I fixed that by executing
make cleandir && make obj && make dependall USETOOLS=never && make install
inside /usr/src/lib
be sure there are not additional errors there!

currently, I was able to rebuild first lib, bin sbin usr.bin, usr.sbin
and then binutils, which was the original goal
As said this improved the situation for c++ but not obj-c. I left a
distribution build running overnight on the laptop, let's see tomorrow
if it finished or if it broke somwhere.